Updating docs, add a few new features to utc.

cmd/utc/README

@@ -1,18 +1,35 @@
 utc: convert times to UTC
 
+Usage: utc [-f format] [-u] [-h] [-z zone] [time(s)...]
+
 utc converts times to UTC. If no arguments are provided, prints the
-current time in UTC. If the only time provided is "-", reads
-newline-separated timestamps from standard input.
+current time in UTC.
 
 Flags:
 
-	-f format	Go timezone format. See the Go documentation
+	-f format	Go timestamp format for input times. See the Go docs
 			(e.g. https://golang.org/pkg/time/#pkg-constants)
 			for an explanation of this format.
+
+			Default value: 2006-01-02 15:04
+
+	-h		Print a help message.
+
+	-o format	Go timestamp format for outputting times. Uses the
+			same format as the '-f' argument; it defaults to
+			the same value as the '-f' argument.
+
+	-u		Timestamps are in UTC format and should be converted
+			to the timezone specified by the -z argument (which
+			defaults to 'Local'). Note that this isn't particularly
+			useful with no arguments.
+
 	-z zone		Text form of the time zone; this can be in short
 			time zone abbreviation (e.g. MST) or a location
-			(e.g. America/Los_Angeles). This has no effect
-			when printing the current time.
+			(e.g. America/Los_Angeles). This has no effect when
+			printing the current time.
+
+			Default value: Local
 
 Examples (note that the examples are done in the America/Los_Angeles /
 PST8PDT time zone):
@@ -41,8 +58,9 @@ PST8PDT time zone):
 	  PST8PDT):
 	  $ utc -u -z EST '2016-06-14 21:30'
 	  2016-06-14 21:30 = 2016-06-14 16:30
-
-
+	+ Using a different output format:
+	  $ utc -o '2006-01-02T15:03:04MST' '2016-06-14 21:30' 
+	  2016-06-14 21:30 = 2016-06-15T04:04:30UTC